1. Field of the Invention
The present invention relates to a method for effectively preventing lead in a lead-containing copper-based alloy from dissolving, which is conventionally used in a faucet.
2. Description of the Related Art
Copper-based alloys such as bronze are currently used for the faucet. Lead is added to the materials of the faucet to improve machinability, ease of casting, and pressure resistance. Lead is distributed in the form of particles in the alloy. Lead is, however, hazardous to humans. When lead contained bronze is used for the faucet, lead particles are dissolved into tap water from the surface of the faucet in contact with the tap water. If the tap water is used as drinking water, lead may build up in the body of human, and may adversely affect the human body. For this reason, the use of lead-free alloys for the faucet is preferred.
However, lead-free copper-based alloys with a low melting point material such as bismuth substituted for lead become costly. Lead-free copper-based alloys without low melting point material result in low machinability. It is currently difficult to produce a lead-free alloy which could satisfy both cost and performance requirements like the conventional faucet alloy containing lead.
Contemplated as means to satisfy both cost and performance requirements is a method for preventing lead in a lead-containing copper-based alloy from dissolving. A technique disclosed in Japanese Open Gazette No. 10-72683 is known.
The disclosed technique uses a strong basic sodium salt such as sodium hydroxide (NaOH) or trisodium phosphate (Na3PO4) to dissolve the lead particles on the surface of the alloy, and the strong basic sodium salt must be handled with the utmost attention. After the process, the strong basic sodium salt must be neutralized. A process bath and tools used in the process must be fabricated of a material that exhibits dissolve resistance to the strong base.
In the disclosed technique, the solution temperature must be kept to be as high as 60 to 95° C. Vapor of the strong base is hazardous to humans and the building, and thus a series of steps needs to be performed in a closed system. Particularly when etching solution containing lead subsequent to the process is disposed or recycled, adverse effect on the humans and the environment is unavoidable because the etching solution is a strong base.